Seats may be relatively complex structures including a combination of sub-systems. For illustration, vehicle seats may include a combination of sub-systems that may be used to position the seat, to provide heating and cooling, to provide an adjustable lumbar support, to adjust a seat contour, and/or to provide adjustable side support in addition to providing a comfortable seating area for occupants. Vehicle seats must provide a safe and comfortable seating area. Comfortable seating is increasingly important for drivers or passengers who spend extended time periods in a motor vehicle.
Various adjustable seat components are known which add to comfort. For illustration, an adjustable lumbar support structure may be integrated into the backrest of a vehicle seat. The adjustable lumbar support structure may be configured such that an amount of curvature and/or an apical position may be adjusted. In addition, massage functions may be provided in which different zones of the lumbar structure are displaced in a cyclical manner to produce a massage effect. Such lumbar support structures frequently include a flexible member which may be formed of a wire framework and/or a plastic member, suspended on a frame of the backrest. Alternatively or additionally, side bolsters of the seat may be adjustable. Adjustable side bolsters may provide a degree of lateral support which is set in accordance with the driver's needs and/or which may be dynamically adjusted, e.g. depending on lateral forces acting upon the driver when driving through a non-straight street. Alternatively or additionally, a contour of the seat backrest may be adjusted, e.g. by changing a curvature at certain sections of the backrest.
Various actuator assemblies may be used for adjusting seat components. Actuator assemblies which utilize traction devices, such as Bowden cables or wires configured to apply a tractive force, provide a high degree of flexibility in positioning the actuator. This is attractive with a view to packaging.
In order to adjust a tension applied by one or several Bowden cables or other traction devices, an actuator which comprises a pulley may be used, for example. The torques which must be exerted onto the pulley as the traction devices become tensioned may impose severe demands onto the output torque and power of a motor and/or the configuration of the speed reduction gearing coupled between the motor and the pulley of the actuator.